1. Field of the Invention
The invention relates to a boiler plant for heat generation.
2. Discussion of Background
The flame stabilization of many modern low-NOx burners is based on the generation of a backflow bubble or backflow zone (=vortex breakdown). If the swirl generator has an unfavorable design, too high a swirl rate causes the desired short backflow bubble to change into a long almost cylindrical backflow zone due to the breakdown of the vortex. When the burner operates without a combustion chamber or with too large a combustion space or with relatively cold combustion chamber walls of a boiler, heat is taken away from the flue gases flowing back in the core. This leads, particularly during startup, to insufficient flame stabilization and, when liquid fuels are used for operation, to inadequate preevaporation of the fuel drops. This behavior may be observed even in the case of burners with passive flue gas recirculation in the combustion space. These problems may lead to flame breakaway or oscillations and make an undesirable special startup procedure necessary. Moreover, as regards heating furnaces, it is necessary to have a very long startup phase with increased emissions, in which the entire boiler, with its relatively high thermal inertia, has to be heated up until the flue gases flowing back are at a sufficient temperature.